Multiple input-multiple output

Radio waves can take multiple paths from the transmitter to the receiver. These multipaths result in interference of the signals and confusion at the receiver. Suppose that we could use these multiple paths constructively. Multiple input-multiple output (MIMO) antenna configurations do just that by creating virtual transmission channels out of the multiple paths. In some tests, MIMO antennas have delivered up to five times the bandwidth in the same spectrum.

MIMO was created at Stanford University by Raleigh and Jones in 1996 and documented in a paper (“Multivariate Modulation and Coding for Wireless Communication”) that drew many comments. Unfortunately, most of these comments were in papers that attempted to debunk the authors’ findings. But, as is often the case, the idea persevered and is now widely accepted.

Raleigh and Jones are the principals in [Airgo], a wireless company that produces MIMO antennas and other wireless products. From a technology standpoint, mathematically and electronically, each multiple path can be uniquely identified and processed so that each path can carry different data. Since the path separation is in time, each multiple path appears as a unique data channel.